Wealth is stuff people want, not what people need. True, if there's shortages of something people really need people will focus on spending their wealth on those things first as there are painful price hikes in basic necessities. But if it's really true that a few numbers of limited people can, using technology, produce everything "really needed" by all of society, the remaining people are then freed to work on whatever else people might want. The fact that people don't "really need" those things doesn't stop anyone from paying for them.

By this article's logic, at the point agriculture was developed and not everyone needed to hunt for food all day, a big chunk of the population should have sat idle and impoverished.